The invention relates to fluorescent articles that comprise durable daylight fluorescent pigment particles, for example, retroreflective articles. Such articles are useful for various applications, such as daytime high visibility signaling and marking, pavement markings, personal safety, and signing.
Fluorescent retroreflective sheeting has been developed to provide increased safety, especially during daytime and periods of reduced visibility. Durable fluorescent sheeting has recently been developed that can withstand the demanding outdoor environments, such as extremes in temperature, chemical challenges from atmospheric pollution and road salt, and photo-reaction involving infrared, visible, and ultraviolet radiation from sunlight. Only certain combinations of fluorescent dye, stabilizers, and matrix polymers provide durability. The matrix polymers found to date may not have the desired features, such as flexibility and economy, sought for many daytime visual signaling and marking applications. Moreover, the relatively expensive fluorescent dyes have been uniformly dispersed throughout past articles, thereby increasing the cost of these prior articles.
Another problem is that on occasion the in-process and final fluorescent sheeting may not meet the stringent demands of customers because of quality and manufacturing problems, such as from start-up and shut-down. Such reject or production waste is expensive and its expense is further exasperated by having to haul it to a landfill. A use for such waste has long been sought.
Highway signing, especially to mark cross-walks, has been a successful application for the recent durable fluorescent retroreflective sheeting. However there remains a need to have the fluorescent color of the sign match that of the pavement marking. Sufficiently durable fluorescent pavement marking articles have not been available to date, although prior attempts have been made, such as by incorporating the fluorescent dye directly into a binder used for the pavement marking.
One process for application of the pavement marking materials involves passing the materials through a high temperature flame to melt the binder onto the highway. Moreover prior fluorescent pavement marking colorants have generally been ultraviolet (UV) activated with the expectation of UV headlights on vehicles. Such UV activated fluorescent materials do not provide for increased safety during daylight and periods of reduced visibility for many transportation safety applications.
Thus the industry seeks durable fluorescent articles for daytime visual signaling and marking applications.
Accordingly, the present invention includes in its first aspect a fluorescent pigment comprising in particle form:
a fluorescent dye including thioxanthone, perylene, perylene imide, xanthene compounds and mixtures thereof; and
a polymeric matrix including polycarbonate, polyester, and mixtures thereof; wherein the fluorescent dye is incorporated into the polymeric matrix.
A second aspect of the present invention includes a fluorescent article, comprising:
a binder having a first major viewing surface; and
fluorescent pigment comprising, in particle form, a fluorescent dye including thioxanthone, perylene, perylene imide, xanthene compounds and mixtures thereof; and
a polymeric matrix including polycarbonate, polyester and mixtures thereof; wherein the fluorescent dye is incorporated in the polymeric matrix; and
wherein at least some of the fluorescent pigment particles are disposed so as to be visible on the first major viewing surface of the binder.
A third aspect of the present invention includes a method of making a fluorescent article, comprising the steps of:
providing at least one fluorescent dye including thioxanthone, perylene, perylene imide, xanthene compounds, and mixtures thereof;
providing a polymer matrix including polycarbonate, polyester, and mixtures thereof;
extruding a mixture of said fluorescent dye and the polymer matrix;
fracturing the extrudate to form a fluorescent pigment in a particle form; and
disposing the fluorescent pigment with a binder to form a fluorescent article.
The third aspect of the present invention may include the additional steps of:
fracturing the binder to yield a binder particulate;
providing microstructured surfaces on the fluorescent pigment to form retroreflective fluorescent pigment;
mixing the fluorescent retroreflective pigment with the binder particulate to form a powder blend; and
flame spraying the powder blend onto a suitable substrate.
Alternatively, the third aspect of the present invention may include the additional steps of:
providing the binder as a liquid dispersion;
providing microstructured surfaces on the fluorescent pigment to form retroreflective fluorescent pigment;
mixing the retroreflective fluorescent pigment with the liquid binder to form a liquid blend;
coating the liquid blend onto a suitable substrate; and
curing the liquid blend onto the substrate to form a retroreflective fluorescent article.
The above fluorescent articles containing fluorescent pigment are especially useful in pavement markings.